doxazosin

Absorption: Well absorbed following oral administration.

Distribution: Unknown.

Protein Binding: 98–99%.

Metabolism/Excretion: Extensively metabolized by the liver.

Half-Life: 22 hr.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
PO‡	1–2 hr	2–6 hr	24 hr
PO-XL‡	5 wk	unknown	unknown

‡Antihypertensive effect.

‡Improved urinary flow and BPH symptoms.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity.

Use Cautiously in:

Hepatic impairment;
GI narrowing (XL only);
Patients undergoing cataract surgery (↑ risk of intraoperative floppy iris syndrome);
OB: Not a preferred antihypertensive during pregnancy ;
Pedi: Safety and effectiveness not established in children;
Geri: Appears on Beers list. ↑ risk of orthostatic hypotension in older adults. Avoid use for treatment of hypertension in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

CV: first-dose orthostatic hypotension, arrhythmias, chest pain, edema, palpitations

Derm: flushing, rash, urticaria

EENT: blurred vision, conjunctivitis, epistaxis, intraoperative floppy iris syndrome

GI: abdominal discomfort, constipation, diarrhea, dry mouth, flatulence, nausea, vomiting

GU: ↓libido, priapism, sexual dysfunction

MS: arthralgia, myalgia

Neuro: dizziness, headache, depression, drowsiness, fatigue, nervousness, weakness.

Resp: dyspnea

Interactions ⬆ ⬇

Drug-drug:

↑risk of hypotension with sildenafil, tadalafil, vardenafil, other antihypertensives, nitrates, or acute ingestion of alcohol.
NSAIDs, sympathomimetics, or estrogens may ↓ effects of antihypertensive therapy.

Route/Dosage ⬆ ⬇

Hypertension

PO (Adults ): 1 mg once daily, may be gradually ↑ at 2-wk intervals to 2–16 mg/day; incidence of postural hypotension greatly ↑ at doses >4 mg/day.

Benign Prostatic Hyperplasia

PO (Adults ): Immediate release: 1 mg once daily, may be ↑ every 1–2 wk up to 8 mg/day; Extended release: 4 mg once daily (with breakfast), may be ↑ in 3–4 wk to 8 mg/day.

Availability ⬆ ⬇

(Generic available)

Tablets: 1 mg; 2 mg; 4 mg; 8 mg
Extended-release tablets: 4 mg; 8 mg

Assessment ⬆ ⬇

Monitor BP and pulse 2–6 hr after first dose, with each increase in dose, and periodically during therapy. Report significant changes.
- Assess for first-dose orthostatic hypotension and syncope. Incidence may be dose related. Observe patient closely during this period and take precautions to prevent injury.
- Monitor intake and output ratios and daily weight, and assess for edema daily, especially at beginning of therapy. Report weight gain or edema.
BPH: Assess patient for symptoms of prostatic hyperplasia (urinary hesitancy, feeling of incomplete bladder emptying, interruption of urinary stream, impairment of size and force of urinary stream, terminal urinary dribbling, straining to start flow, dysuria, urgency) prior to and periodically during therapy.

Implementation ⬆ ⬇

PO: Administer daily dose at bedtime.
- DNC: XL tablets should be swallowed whole; do not break, crush, or chew.
Hypertension: May be administered concurrently with a diuretic or other antihypertensive.

Patient/Family Teaching ⬆ ⬇

Emphasize the importance of continuing to take this medication, even if feeling well. Instruct patient to take doxazosin at the same time each day. Take missed doses as soon as remembered unless almost time for next dose. Do not double doses.
- May cause drowsiness or dizziness. Advise patient to avoid driving or other activities requiring alertness until response to medication is known.
- Caution patient to change positions slowly to decrease orthostatic hypotension. May cause syncopal episodes, especially within first 24 hr of therapy, with dose increase, and with resumption of therapy after interruption.
- Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to avoid concurrent use of alcohol or OTC medications and herbal products, especially cold preparations, without consulting health care professional, especially cough, cold, or allergy remedies.
- Advise patient to notify other physicians of drug therapy.
- Advise male patient to notify health care professional if priapism or erection of longer than 4 hr occurs; may lead to permanent impotence if not treated.
- Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.
- Emphasize the importance of follow-up visits to determine effectiveness of therapy.
Hypertension: Instruct patient and family on proper technique for BP monitoring. Advise them to check BP at least weekly and report significant changes.
- Encourage patient to comply with additional interventions for hypertension (weight reduction, low-sodium diet, smoking cessation, moderation of alcohol consumption, regular exercise, and stress management).

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇